ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Other Comprehensive Income (Loss), before Reclassification Adjustments and Tax [Abstract]
Unrealized gain (loss) on investment securities	$ (182,479)	$ (39,658)
Retirement obligation	0	0
Total	(182,468)	(39,658)
Other Comprehensive Income (Loss) Reclassifications before Tax [Abstract]
Realized gain (loss) on securities available-for-sale	(3)	(166)
Retirement obligation	(325)	(525)
Total	(328)	(691)
Transactions Pre-tax
Unrealized gain (loss) on investment securities	(182,476)	(39,492)
Unfunded pension obligation	325	525
Total	(182,140)	(38,967)
Transactions Tax-effect
Unrealized gain (loss) on investment securities	40,075	8,524
Retirement obligation	21	(120)
Total	40,096	8,404
Transactions Net of tax
Unrealized gain (loss) on investment securities	(142,401)	(30,968)
Retirement obligation	346	405
Total	(142,044)	(30,563)
Balances Net of tax
Unrealized gain (loss) on investment securities	(121,363)	42,608	$ 21,038	$ 73,576
Retirement obligation	(20,500)	(24,507)	(20,846)	(24,912)
Total	(142,477)	18,101	(433)	$ 48,664
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	11
Other Comprehensive Income (Loss), Reclassification, Foreign Currency Transaction	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	11
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	11
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(614)		$ (625)
Accumulated other comprehensive income (loss)
Transactions Net of tax
Total	$ (142,044)	$ (30,563)